Should I do two rib roasts?

I'm doing a 15 lb rib roast tonight. Half the family is in the rare camp and half is in the medium-medium well (i know ...) camp. I'm thinking of cutting it half and cooking one piece an hour longer to try to accommodate everyones taste. Is there a better approach? I am planning to cook it in a hot oven initially and then reduce the heat. How do I do this with two roasts, put them both in the hot oven initially and then let the rare roast sit at room temp for an hour? Or do the medium one first, then pull it out and reheat the oven again? I remember reading once about a chef who would sear the outside with a torch before roasting. This would solve the problem.. Has anyone tried this?